Recuperative boiler



July 1, 1969 a. M. A. MARIETE ETAL 3,452,721

RECUPERAT IVE BOILER Filed Sept. 14, 1967 1 Mvemoks 1 mrow/e ys United States Patent O Inf. ci. lizzb 1/18 U.S. Cl. 122-32 12 Claims ABSTRACT F THE DISCLOSURE This invention relates to an industrial `recuperative =boiler adapted to utilize a heating uid at high temperature and under high pressure, which comprises a vertically 'disposed generally cylindrical body provided with a median inlet orifice and at its opposite ends `with lateral outlet orifices, and a nest of water tubes the opposite ends of which are respectively connected to a steam casing o'bturating the upper end of said body and supporting said nest, and to a water casing slid-ably housed within the lower end of said body and obturating the same through the intermediary of a fluid-tight expansion joint.

Many industrial processes, and especially the processes applied in the chemical industries and those related to the latter, produce important quantities of high-temperature gases which it is important to cool do-wn substantially to allow their use during a subsequent stage of the process or merely to discharge them in the atmosphere. It is obviously advantageous to recover the sensible heat of these gases to produce at low costs for instance steam utilisable either in the very process or to supply the various appliances of the production device.

Thus, and for instance, the manufacturing of many synthetic products includes nowadays the preparatory production of a synthetic gas which is often put out at a high temperature (for instance ranging about 1,000 C.) and under an important pressure (for example in the range of 30 bars). The subsequent treatment of these gases with respect to the requirements of the synthetic process may need a substantial lowering of their temperature, which should for instance be brought down from 1,000 C. to 400 C.

It is quite obvious that the recovering of the sensible heat from a gas presenting such .pressure and temperature characteristics requires a special boiler, of a simple and robust construction apt to sustain high mechanical and thermal stresses; moreover, such a boiler should be fluidtight and allow an easy maintenance to avoid any loss or contamination of the gas securing its heating. Finally, especially in case where the steam supplied by the boiler is designed to be used in the synthetic process, it is advantageous to produce it under a high pressure, which may be for instance above 150 bars.

The present invention relates to an industrial recuperative boiler, the new, simple and solid construction of which is designed to meet the most exacting requirements.

An industrial recuperat-ive boiler conformable to the invention, designed to produce for instance saturated steam under a high pressure by using at least partly the sensible heat of a heating uid at an important temperature and under a high pressure, is remarkable especially in that it comprises a cylindrical tubular body with a vertical axis, said body being provided in its central area with a median lateral orifice for the admission of the aforesaid heating fluid and at its opposite ends rwith lateral orifices to exhaust said heating fluid, a nest of water tubes, said nest being coaxial with said body, the upper ends of said tubes being rendered solid with a tubular plate integral with an emulsion or steam casing obturating the top end of said body and supporting said nest, while the lower ends of said tubes are rendered solid `with a tubu-lar plate integral with a water casing housed Within sa'id lbody and obturating the lower end of the latter by means of a uid-tight expansion joint allowing a free axial shifting of said water-casing.

It will be readily appreciated that the construction and the arrangement selected for the body of the boiler in accordance with the invention allow it to resist effectively to very high pressures, and that the steadfast assembly of the different units constituting its water and steam circuits on the one hand secures a reliable operation and, on the other hand, permits to remove the whole of said units, so that the maintenance of the boiler becomes extremely easy.

In other respect-s, the location selected for the admission and exhaust orifices for the heating `fluid results in that the latter is divided in two symmetrical streams so that both tubular plates obturating the ends of the boiler body receive but relatively cool gases and may consequently not be subjected to any damaging stresses.

According to another feature of the invention, the aforementioned boiler body comprises at least one bypass orifice provided between the aforesaid admission and exhaust orifices, a portion of said heating fluid being possibly derived thru said 'by-pass orifice in order to regulate the output temperature of said fluid.

According to still another feature of the invention, the heat-exchange nest of the aforementioned boiler is provided with axially spaced transverse deilectors forming baille-plates on the path of said heating uid.

Advantageously, the raforementioned deectors are made up by alternately arranged small lids and annular diaphragms.

These arrangements, which obviously aim at securing locally a heating fluid circulation transverse to the Water tubes, may of course be combined with other means for guiding said Huid.

Many other features and advantages of the boiler in accordance with the invention will appear more clearly by reading the following detailed description of an embodiment, given only as an example which should not be considered as limiting this invention, said embodiment being illustrated by the accompanying drawing, the single figure of which represents in a longitudinal axial section a recuperative boiler according to the invention.

The recuperative boiler hereafter described as an example embodying this invention is designed to supply saturated steam under a very high pressure, for instance under bars, said boiler being for example heated by a gas of synthesis produced under a 30 bars pressure at a temperature of about 1,000 C., said temperature having then to be reduced to about 400 C. for example. These heating-gas characteristics correspond to important heatexchange factors which allow the use of simple structural arrangements, especially of a water-steam circuit of a type including water tubes and a natural circulation.

The illustrated boiler comprises essentially 4a body 10 made up by a thick metal covering 11 having an essentially tubular general configuration and vertical axis, the middle area of said covering being provided with a lateral orifice 12 for the admission of the heating gas G, while its top and bottom ends are provided with lateral orifices, respectively 13 and 13", allowing to exhaust said gas. The inner surface of the metal covering 11 is entirely covered by a fitting 14 of a refractory and insulating material, the thickness of which is locally increased on both sides of the heating-gas admission orifice 12, said additional thickness increasing locally the diameter of the metal covering 11 without modifying the inner diameter of the fitting, for the hereinafter given reasons.

The upper end of the metal covering 11 surrounding the Iboiler body comprises an external flange 15, while its bottom end comprises a conical projection 16 at the end of which is fastened by means of Huid-tight expanding bellows 17 an annular member 18 provided with an internal fiange 19.

The water and steam circuit comprises essentially a multi-tubular exchanging nest 20, the external shape 0f which is cylindrical with a diameter smaller than the internal surface of the boiler body, said nest being coaxial with the latter. Advantageously, the exchanging nest 20 is constituted by mere straight vertical water tubes 21, arranged in a dense network which may for instance be of the centered hexagonal mesh type. The bottom ends of the water tubes 21 are raked upon a tubular plate 31 integral with a water casing 30 installed in the bottom area 16 of the boiler body 10, said casing comprising at its lower end, on the one hand, an axial orifice 32 for the water supply and, on the other hand, an external ange 33 used to support it and tightly fastened upon the iiange 19 of the annular end piece 18 of the boiler body 10.

The top ends of the water tubes 21 are raked in a similar way upon a tubular plate 41 integral with a steam or emulsion casing 40, exhibiting a general cylindrical shape and comprising a lateral connection 42 to exhaust the vapor V as well as a removable cover 43. The casing 40 rests and is tightly fastened upon the external flange of the boiler body 10, so that it may support thus the exchanging nest and the water casing 30 solid with said nest.

It appears at once from the preceding description that the units of the water and steam circuits (ie. the exchanging nest 20, the water casing and the emulsion casing make up a solid whole which may be sunk as a single piece into the boiler body 10 during the assembly and, in a similar way, removed to allow for instance a complete internal cleaning of said boiler body.

Besides, it appears that the heating gas G is divided within the boiler into two symmetrical streams respectively exhausted by the orifices 13 and 13; thus, in order to balance the output temperatures of the heating liuid and taking into account the different exchanging conditions met by each of said fiuid streams, one may, either provide the admission orifice 12 at unequal distances from the exhaust orifices 13' and 13, or again provide the latter with different passage diameters so as to make the circulation speed proportional to the two gas streams.

Besides, as represented, the boiler body 10 may be provided with by-pass orifices 51 and 52 located upstream of the respective exhaust orifices 13 and 13l and thru which controlled portions G and G of the heating fluid (said portions being not necessarily identical) may be derived, so as to adjust for each case the output temperature of said fiuid when it is exhausted thru the orifices 13 and 13.

The invention aims also to provide means liable to improve the thermal exchange conditions between the heating gas G and the water tubes composing the nest 20, by obliging said gas to follow a path passing thru baieplates, most of said plates being transversely arranged with respect to said tubes.

As represented, these means are composed of axially spaced transverse defiectors, carried by the water tubes 21 and alternately made up by circular lids 61, arranged in the axis of the nest, and by annular diaphragms 62 the external periphery of which comes practically into contact with the internal refractory coating surface 14. Advantangeously, the endmost defiectors of each bafieplate, especially those framing the gas admission orifice 12, are made up by diaphragms securing a proper penetration of the heating gas into the center of the nest.

It appears radily that these arrangements condition the flowing of the heating gas within the nest so as t0 improve the thermal balance between the different tubes composing it, especially in the central part of said nest.

These arrangements may be carried out separately or again combined with other guiding means such as for instance the defiectors 25 and 25 installed at the ends of the nest, respectively before the exhaust orifices 13 and 13". Each deflector is made up by a part of a sleeve surrounding the exchanging nest 20 opposite to the exhaust orifice. It will be understood that the baffle thus constituted obliges the heating gas to maintain its longitudinal motion within the exchanging nest 20 up to the end of the latter, and to pass then thru the peripheral annular space towards the exhaust orifice. Advantageously the sleeves 25 and 25" are worked out of stainless steel sheets solid with the peripheral tubes of the exchanging nest 20 and consequently the aforesaid unit making up the water-steam circuit.

The operation of the described and illustrated boiler is the following:

The water E fed into the water casing 30 thru the axial admission orifice 32 passes thru the tubular plate 31 into the water tubes 21. The calories provided by the heating gas G make appear a water and steam emulsion in these water tubes, the lower density of which creates an ascensional force securing the natural circulation of the water, then of the emulsion towards the emulsion casing 40 and from there towards an external ask including means for the separation of the steam and for its subsequent use.

The simple geometrical structure of the boiler body 10 allows an easy working out of its metal covering 11 from substantially thick sheets assembled by welding, so that said boiler body is apt to resist to high internal pressures while remaining perfectly Huid-tight. Besides, taking into account its vertical position, said body may constitute a self-supporting structure, so that the installation of the boiler is made much easier. Moreover, the simple geometrical shape of the boiler body 10 allows also to provide it with an integral refractory coating 40` which will make it resistant to high temperatures and possible to corrosion by the heating gas G.

By composing the water-steam circuit as a single suspended unit many essential advantages may be gained when considering especially the balancing out of the expansions (which may not be avoided) in the Water tubes 21. IIndeed, considering the high temperature of the heating gas and the great relative length of the exchanging nest, these expansions would lead to excessive mechanical stresses if both ends of the nest were fastened. In contrast, according to the invention, these expansions are easily absorbed by the expansion joint 17 provided for this purpose at the lower part of the boiler body 10 in the described and illustrated example of embodiment. Of course, in alternate embodiments, this joint could be of a different type and in a different arrangement. Moreover the construction as a single unit of the water-steam circuit offers many other advantages, directly related to its easy installation and disassembly, which allow to visit very often the boiler body, especially in order to make sure of a good upkeep of the refractory coating and possibly to remove any deposits capable of contaminating the heating gas. It should also be noted that the straight tubes 21 composing the exchanging nest are easily reached, with or without a disassembly of the water-steam circuit, on the one hand, from the axial water admission orifice 32, and on the other hand, thru the removable cover 43 of the emulsion casing 40. These arrangements allow to clean easily the inside of a tube or again to replace Such a tube.

Be it well understood that the invention is by no means limited to the described and illustrated method of embodiment, which has been given only by way of an example. `In particular, this invention is intended to cover all means constituting technical equivalences of the described means as well as combinations of the latter.

What we claim is:

1. A boiler for utilizing a heating fluid at high temperature and pressure, comprising: an upright generally cylindrical tubular body having an upper bearer flange and provided intermediate its ends with a lateral inlet orifice and near said ends with respective lateral outlet orifices for said heating fiuid; an annual member located under said body and having an internal flange; an expansion joint sealingly fastening said annular member to said body; an elongated assembly insertable within said body and annular member from the upper end thereof and consisting of an upper steam casing, a lower water casing and an intermedite nest of tubes, said upper casing and lower casing being arranged, when inserting said assembly within said body, to rest respectively on said bearer ange and internal fiange, and to be tightly fastened thereto.

2. A boiler according to claim 1 wherein said body consists of a sheet-metal covering provided with an inner lining of heat-insulating refractory material.

3. A boiler according to claim 1 wherein the diameter of said covering is locally increased around said inlet orifice, thereby allowing for a local increase of the thickness of said lining without vmodifying its inner diameter.

4. A boiler according to claim 3, wherein the respective cross-sectional areas of said outlet orifices, are determined in relation to the axial position of the inlet orifice so as to balance the temperatures of said heating fluid at both said outlet orifices, and wherein the aggregate crosssectional area of the outlet orifices is substantially equal to that of the inlet orifice.

5. A boiler according to claim 4, wherein said body comprises at least one by-pass orifice operatively disposed between said inlet orifice and one of said outlet orifices, through which a controllable fraction of said heating fluid may be derived.

6. A boiler according to claim 1 wherein said nest is built up from water tubes extending generally longitudinally of said body, and is provided with axially spaced, transverse defiectors.

7. A boiler according to claim 6, wheerin said deliectors consist of plain discs and annular diaphragms disposed alternately.

8. A boiler according to claim 7, wherein those of said deflectors which lie in the immediate vicinity of said inlet and outlet orifices consist of annular diaphragms.

9. A boiler according to claim 8, wherein said annular` diaphragms adjacent to said outlet orices are provided with a part-cylindrical extension disposed outside of said nest in front of said outlet orifices.

10. A boiler according to claim 1, wherein said steam casing is provided with a lateral steam exhaust orifice and is closed by a removable end cover, and wherein said water casing terminates at an axial water admission orifice provided with an external fiange sealingly connectable to the internal flange of said annular member.

11. An industrial recuperative boiler adapted to utilize a heating uid at high temperature and under high pressure comprising; a vertically disposed, generally cylindrical tubular body provided in its central portion with a lateral inlet orifice and at its opposite ends with a pair of lateral outlet orifices for said heating fluid; an annular member located under said body; an expansion joint sealingly fastening said annular member to said body; a nest of water tubes coaxially arranged within said body; a steam casing; a water casing; an upper tube plate and a lower tube plate rigidly connected respectively to the upper and lower ends of said tubes, said upper plate forming an integral part of said steam casing and obturating the upper end of said body and resting upon the same for supporting said nest, and said lower plate forming an integral part of said water casing, said `water casing being slidably housed Within the lower end of said body and obturating said annular member; and axially spaced, transverse deflectors disposed across said tubes.

12. A boiler according to claim 11, wherein said deflectors consist of plain discs and annular diaphragms in alternance.

References Cited UNITED STATESPATENTS 1,892,778 l/1933 Black -161 XR 1,917,595 7/1933 McDerniet 165-161 XR 2,590,465 3/1952 Ris 165-169 XR KENNETH W. SPRAGUE, Prma'ry Examiner.

U.S. Cl. X.R. 165-158 

